The present invention relates to a valve body for controlling a medium flowing through a valve, which valve comprises a valve housing, in which the valve body, which has at least one gasket for sealing cooperation with the valve housing or where appropriate with a cage arranged in the valve housing, is axially displaceable by means of a spindle in the direction towards and from a valve seating in the valve.
For certain valve applications currently on the market it is required by the person using these that the valve should be tight, which normally gives a unidirectional very strong setting force. To achieve as weak setting force as possible one uses a so called balanced valve, which is achieved by a connection channel extending between the low pressure side of the valve body and the confined volume, which is above the valve body and within the valve lid. Up to now, these two mentioned variants of valve applications have not been possible to combine completely.
The object of the present invention, therefore, is to provide a tight valve body and more particularly a balanced, tight valve body, which consists of a complete valve package, in which the components of the valve body completely seal, when the valve body is just before and/or in its closing position in the valve housing at the same time as such a small frictional wearing as possible arises on the gasket, when the valve is working outside its closing positions. The characterizing features of the invention are stated in the accompanying claims.
Thanks to the invention a new type of valve body for controlling a medium of the above mentioned kind flowing through a valve, which valve body in an excellent manner fulfills its purposes and in addition at the same time is simple and cheap to manufacture. The valve body according to the invention specifically has a press member, preferably In the form of a sleeve, which runs externally on a central valve cone, and a gasket made of a material that when influenced by forces from the sleeve can expand radially outwardly as well as inwardly. In a preferred embodiment the gasket is fixable in its position with the aid of a split ring, which is axially locked through assemblage in a groove in the valve cone. Thanks to this solution, when the valve cone reaches its closing position against the valve seating it results in that the sleeve slides on the valve cone and transfers forces against and compresses the gasket, which then expands radially in its space defined by the sleeve, the split ring, the valve cone and the wall present within the valve. The gasket in question creates a strong surface pressure on the surfaces defining the closed volume.
In the opened valve position when the valve is in operation the sleeve is no longer in contact with the valve seating, wherein the sleeve no longer transfers any forces that influences the gasket and will not create any surface pressures at its confining surfaces as well. By eliminating or delimiting the surface pressure against the gasket, the friction against the present valve wall, towards which the valve body runs, will be very low, wherein also the required setting force of the valve can be kept low at the same time as the wear of for example the gasket is radically reduced. By the structure in question only one force against the gasket is created when the valve is closed whereas when the valve is open and working this force against the gasket has been completely eliminated, wherein no frictional forces can be generated at the same time as the structure in question compensates the wear of the gasket through the axial movement of the sleeve.